Although not limited thereto, the invention relates more particularly to a valve for bottles or reservoirs containing liquefied or compressed gas. In this kind of valve, the connecting means may be a rod and the means of limiting the movement in the direction of opening generally includes one or two pins passing through the body of the valve in the transverse direction at right angles to the movement of the rod and tangentially with respect to the latter. For this, the rod comprises, in its central region, an annular constriction allowing the passage of the two pins and allowing the rod to turn. These two pins and the base of the constriction form stops and mating stops defining the end of travel of the rod and halting the valve-opening movement.
The disadvantage of this known system is that at the end of the movement and given that the valve is generally opened wide, the end of the constriction of the rod approaches the two pins tangentially because of the turning of the rod. In consequence, contact between the rod and the pin or pins is a friction or rubbing contact, that is to say occurs with progressive binding, or even jamming of the valve in the open position.
This binding or jamming of the valve requires a great deal of manual force when closing the valve and encourages the use of a tool, such as pliers. This may, however, be the root of carelessness and has already caused accidents when closing the valve. Thus, when the valve is jammed in this way, it is sometimes the case that the operator does not know whether the valve is open or closed, and an operator has already, when wishing to slacken off the valve using a tool, turned the operating member in the wrong direction, that is to say in the direction for opening, with the result of breaking the head of the valve. This may obviously constitute a serious danger if the gases are harmful or explosive.
To avoid such jamming, document EP 1 124 081 A1 proposes a valve of the kind described in the preamble. In this valve, there is no rubbing contact between the stop and the mating stop and there is therefore no risk of the valve binding or jamming. The operator can easily shut-off the valve without exerting excessive force and without the risk of mistaking which direction to turn in and of binding the valve still further.
During opening, and in the penultimate turn of the operating member, the stop and the mating stop do not yet come into contact, which means that when they stop the turning of the operating member, they are in mutual contact over a height which is shorter than the pitch of the screw threads between the rotary elements and the body of the valve.
However, a valve as described in the aforementioned document does not operate reliably unless the stop and the mating stop contact over a large part of their mutual surfaces, that is to say over most of their axial length. If, for example, the stop and the mating stop are, the penultimate time the stop passes the mating stop, still separated by an axial distance which is barely smaller than the pitch of the screw which axially moves the moving stop, then the two stops will come into mutual contact only via their respective axial edges in order to stop the turning. Now, this may, in the long-term, lead to wear on their contacting edge and finally culminate in frictional contact, placing the valve back in the problematical situation described above.
This risk is therefore dependent on parameters which are of deciding importance to the area of contact between the stop and the mating stop. These are, in this instance, the pitch of the screw which axially moves the moving stop, the respective angular positions of the moving stop and of the mating stop, and the manner of assembly.